Raptor

The wizards traveled back in time during their experiments. It took them immense and unimaginable effort, and was one of the most difficult things they did. When they opened the time travelling portals, hordes of raptors came out. The wizards decided to ride some of them, while others tried to eat the wizards and had to be destroyed. Most of them, the ones who have reproduced enough to become one of the predators of Minecraftia, do not allow wizards to ride them and think a nice juicy Steve would be tastier than the wizards who brought them into the future.

The only fruit of their time travelling work was bringing back these dinosaurs. The wizards never unleashed any T-Rexes or any other dinos as they wanted to, but raptors have become a top predator, and they'll eat you and your babies if you don't kill them.

Striped, speedy, and somewhat sneaky, raptors are extremely fast, (In fact, faster than any mob, with the possible exception of the Roflconda), aggressive, and can pose a notable threat to those who wield ranged weapons as their primary method of attack, (Especially Rangers, due to the bow's slow rate of fire and slight inaccuracy). Raptors deal physical damage, and, similar to spiders, almost always jump while charging at their foe. Wizards can ride Raptors, and if the Wizard teleports, the Raptor will come with it.

Due to their hit box they have problems in closed areas like 1x2 tunnels. This can be exploited to great length when dealing with towers and dungeons.
Kiting them is also an option, and leap (as a ranger) is a nice counter to keep the distance. The last thing you want to do in a dungeon is get swarmed, but if you do, try not to panic. Find tight areas and the raptors will have trouble fitting through. Raptors can be exceedingly annoying when you are trying to escape.